export function appendAttachments(container, attachments = []) {
    if (!attachments.length) return;
    const gallery = document.createElement("div");
    gallery.className = "message-images";
    for (const item of attachments) {
        if (!/^[a-f0-9-]{36}$/.test(item.id)) continue;
        const link = document.createElement("a");
        link.href = `/attachments/${item.id}`;
        link.target = "_blank";
        link.rel = "noopener";
        const image = document.createElement("img");
        image.src = link.href;
        image.alt = item.originalName || "Attached image";
        image.loading = "lazy";
        link.append(image);
        gallery.append(link);
    }
    container.append(gallery);
}

export function createAttachmentComposer({onChange, onError}) {
    const button = document.getElementById("attachImage");
    const picker = document.getElementById("imagePicker");
    const preview = document.getElementById("uploadPreviews");
    const composer = document.querySelector(".input-container");
    let items = [];
    let busy = false;
    let limits = {maxSizeMb: 10, maxFiles: 5};
    fetch("/uploads/config").then(r => r.ok ? r.json() : limits).then(value => { limits = value; }).catch(() => {});
    const render = () => {
        preview.replaceChildren();
        preview.hidden = !items.length;
        for (const item of items) {
            const card = document.createElement("div");
            card.className = "upload-preview";
            const image = document.createElement("img");
            image.src = item.preview;
            image.alt = item.file.name;
            const label = document.createElement("span");
            label.textContent = `${item.file.name} — ${item.error || (item.metadata ? "Ready" : "Uploading…")}`;
            card.append(image, label);
            if (item.error) {
                const retry = document.createElement("button");
                retry.type = "button"; retry.textContent = "Retry"; retry.disabled = busy;
                retry.onclick = () => { void upload(item); };
                card.append(retry);
            }
            const remove = document.createElement("button");
            remove.type = "button"; remove.textContent = "×"; remove.disabled = busy;
            remove.setAttribute("aria-label", `Remove ${item.file.name}`);
            remove.onclick = () => {
                items = items.filter(v => v !== item);
                item.controller?.abort(); URL.revokeObjectURL(item.preview);
                if (item.metadata) void fetch(`/attachments/${item.metadata.id}`, {method: "DELETE"});
                render();
            };
            card.append(remove); preview.append(card);
        }
        onChange();
    };
    const upload = async item => {
        item.error = null;
        item.controller = new AbortController();
        render();
        try {
            const form = new FormData(); form.append("image", item.file);
            const response = await fetch("/uploads", {method: "POST", body: form, signal: item.controller.signal});
            const result = await response.json();
            if (!response.ok) throw new Error(result.error || "Upload failed");
            item.metadata = result;
            if (!items.includes(item)) void fetch(`/attachments/${result.id}`, {method: "DELETE"});
        } catch (error) {
            if (error.name !== "AbortError") item.error = error.message || "Upload failed";
        }
        render();
    };
    const add = files => {
        if (busy) return;
        for (const file of files) {
            if (items.length >= limits.maxFiles) { onError(`Attach at most ${limits.maxFiles} images`); break; }
            if (!["image/png", "image/jpeg", "image/webp"].includes(file.type)) { onError("Use PNG, JPEG or WebP images"); continue; }
            if (!file.size || file.size > limits.maxSizeMb * 1024 * 1024) { onError(`Images must be non-empty and at most ${limits.maxSizeMb} MB`); continue; }
            const item = {file, preview: URL.createObjectURL(file)};
            items.push(item); void upload(item);
        }
    };
    button.onclick = () => picker.click();
    picker.onchange = () => { add(picker.files); picker.value = ""; };
    composer.addEventListener("dragover", event => {
        if (event.dataTransfer.types.includes("Files")) { event.preventDefault(); composer.classList.add("image-drag-target"); }
    });
    composer.addEventListener("dragleave", () => composer.classList.remove("image-drag-target"));
    composer.addEventListener("drop", event => {
        event.preventDefault(); composer.classList.remove("image-drag-target"); add(event.dataTransfer.files);
    });
    composer.addEventListener("paste", event => {
        const images = [...(event.clipboardData?.files || [])].filter(file => file.type.startsWith("image/"));
        if (images.length) { if (!event.clipboardData.getData("text/plain")) event.preventDefault(); add(images); }
    });
    return {
        get attachments() { return items.filter(v => v.metadata).map(v => v.metadata); },
        get pending() { return items.some(v => !v.metadata); },
        setBusy(value) { busy = value; button.disabled = value; picker.disabled = value; render(); },
        clear() { items.forEach(v => URL.revokeObjectURL(v.preview)); items = []; render(); }
    };
}